1. Field of the Invention
The invention relates to an electric circuit, in particular for a medium-voltage power converter, having at least four semiconductor switches that form a series circuit and are connected to poles of a direct voltage, a diode being connected in antiparallel with each of the semiconductor switches, and a capacitor being connected in parallel with the two middle semiconductor switches of the series circuit, having a pole of an output voltage that is connected in the middle to the series circuit, and having a control unit for sequentially driving the semiconductor switches. The invention likewise relates to a corresponding method for operating an electric circuit, in particular for a medium-voltage power converter.
2. Related Art
Such an electric circuit is generally known and is used, in particular, in medium-voltage power converters. The direct voltage is connected to the outer two taps of the semiconductor switches forming a series circuit, and the output voltage is present at their common, middle tap. The semiconductor switches are switched by a control unit one after another into their conducting and their blocking states. The resulting AC voltage includes of a sequence of pulses.
Asymmetric voltage splits between the various semiconductor switches can occur because of the ever present differences between the performance quantities of the semiconductor switches connected in series, and this can lead to overloadings of the individual semiconductor switches. Likewise, as a consequence of switching over the semiconductor switches the voltage jump of the individual pulses of the output voltage is very large, and this can lead to overvoltage peaks. These disadvantages are removed or at least lessened in the case of known power converters with substantial outlay on circuitry.